The present invention relates to a press for forming a long and narrow metal or synthetic resin plate, sheet or strip into a beam of L-shaped section free from convex or concave warp.
In particular, the present invention relates to a press-forming apparatus comprising a laterally long fixed frame, a movable frame of a length substantially equal to that of the fixed frame, a space provided adjacent and parallel to a die mounting surface of the movable frame, a plurality of small hydraulic cylinders (hereinafter, referred to as the "deflection cylinders" ) provided in the space independently from the main hydraulic cylinders of the movable frame for compensating for deflection of the fixed frame and the movable frame during pressing and pressure-fluid paths for the small hydraulic deflection cylinders connected to the pressure-fluid paths of the main hydraulic cylinders.
In general, press-forming apparatuses for press-forming a long and narrow metal or synthetic resin strip sheet or plate (referred to as the "material" hereinafter) into a beam L-shaped in section utilize a pair of parallel disposed C-shaped support frames as a base structure support for the fixed and the movable frames, a fixed frame and a movable frame which is vertically movable by a crank mechanism and other mechanical mechanisms or hydraulic or air cylinders.
In the conventional apparatus for this purpose, there is a very important disadvantage irrespective of the driving mechanisms or the guiding mechanisms used to operate the movable frame. This disadvantage is related to the deflection of the fixed frame and the movable frame caused by the pressing force exerted thereon and the resilient force of the material to be pressed and appears as an undesired deformation of the pressed material. The undesired deformation appears as either a concave or a convex warp of the center portion of the pressed material.
In order to eliminate such undesired deformation it is usual to make the rigidities of the fixed frame and the movable frame sufficient to withstand the deflection force, to preliminarily machine a crown into the movable frame so that when the frame is deflected the surface thereof becomes flat or to shim the dies mounted on the frame. These methods are, however, not satisfactory and a more effective method for compensating for the deflection of the frames is required.
An object of the present invention is to provide a press-forming apparatus for press-forming a long material into a beam of L-shaped section without concave or convex warp of the center portion thereof.